Reaction: (1) spheroidene + 2 reduced ferredoxin [iron-sulfur] cluster + 2 O2 = spheroiden-2-one + 2 oxidized ferredoxin [iron-sulfur] cluster + 3 H2O (overall reaction)
(1a) spheroidene + reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = 2-hydroxyspheroidene + oxidized ferredoxin [iron-sulfur] cluster + H2O
(1b) 2-hydroxyspheroidene + reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = 2,2-dihydroxyspheroidene + oxidized ferredoxin [iron-sulfur] cluster + H2O
(1c) 2,2-dihydroxyspheroidene = spheroiden-2-one + H2O (spontaneous)
(2) spirilloxanthin + 2 reduced ferredoxin [iron-sulfur] cluster + 2 O2 = 2-oxospirilloxanthin + 2 oxidized ferredoxin [iron-sulfur] cluster + 3 H2O (overall reaction)
(2a) spirilloxanthin + reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = 2-hydroxyspirilloxanthin + oxidized ferredoxin [iron-sulfur] cluster + H2O
(2b) 2-hydroxyspirilloxanthin + reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = 2,2-dihydroxyspirilloxanthin + oxidized ferredoxin [iron-sulfur] cluster + H2O
(2c) 2,2-dihydroxyspirilloxanthin = 2-oxospirilloxanthin + H2O (spontaneous)
(3) 2-oxospirilloxanthin + 2 reduced ferredoxin [iron-sulfur] cluster + 2 O2 = 2,2'-dioxospirilloxanthin + 2 oxidized ferredoxin [iron-sulfur] cluster + 3 H2O (overall reaction)
(3a) 2-oxospirilloxanthin + reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = 2'-hydroxy-2-oxospirilloxanthin + oxidized ferredoxin [iron-sulfur] cluster + H2O
(3b) 2'-hydroxy-2-oxospirilloxanthin + reduced ferredoxin [iron-sulfur] cluster + O2 + 2 H+ = 2',2'-dihydroxy-2-oxospirilloxanthin + oxidized ferredoxin [iron-sulfur] cluster + H2O
(3c) 2',2'-dihydroxy-2-oxospirilloxanthin = 2,2'-dioxospirilloxanthin + H2O (spontaneous)
For diagram of reaction click here or click here.
Glossary: spheroidene = 3,4-didehydro-1-methoxy-1,2,7',8'-tetrahydro-ψ,ψ-carotene
Other name(s): CrtA; acyclic carotenoid 2-ketolase; spirilloxanthin monooxygenase; 2-oxo-spirilloxanthin monooxygenase
Systematic name: spheroidene,reduced-ferredoxin:oxygen oxidoreductase (spheroiden-2-one-forming)
Comments: The enzyme is involved in spheroidenone biosynthesis and in 2,2'-dioxospirilloxanthin biosynthesis. The enzyme from Rhodobacter sphaeroides contains heme at its active site [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Lee, P.C., Holtzapple, E. and Schmidt-Dannert, C. Novel activity of Rhodobacter sphaeroides spheroidene monooxygenase CrtA expressed in Escherichia coli, Appl. Environ. Microbiol. 76 (2010) 7328-7331. [PMID: 20851979]
2. Gerjets, T., Steiger, S. and Sandmann, G. Catalytic properties of the expressed acyclic carotenoid 2-ketolases from Rhodobacter capsulatus and Rubrivivax gelatinosus, Biochim. Biophys. Acta 1791 (2009) 125-131. [PMID: 19136077]